A single-frequency network refers to a wireless transmission system in which the same data is transmitted from multiple transmit stations simultaneously on the same frequency band. To be more exact, an identical signal is transmitted simultaneously from the transmit stations. When a radio receiver receives the data signals transmitted from the multiple base stations, a received data signal is a combination of the transmitted data signals. This is because the data signals transmitted on the same frequency band simultaneously sum up in a radio channel before they are received at the radio receiver. Since the transmitted data signals summed in the radio channel are identical, the radio receiver experiences the signals as multipath-propagated signals. Naturally, each of the transmitted signals propagates to the radio receiver through multiple paths in the radio channel, causing more multipath components.
For example, let us assume that two transmit stations transmit the same data signal simultaneously on the same frequency band to a radio receiver and that each of the two transmitted data signals propagate to the radio receiver through 4 different paths. Accordingly, the radio receiver experiences a received radio signal as having 2*4=8 multipath components.
The single-frequency network may be seen as a type of handover in which signal combining takes place in the radio channel. The single-frequency network concept may be used for extending coverage in telecommunication systems where a symbol time is long with respect to an expected signal arrival time difference. A system using orthogonal frequency division multiplexing (OFDM) as a transmission scheme is a good candidate for the single-frequency network concept due to the long duration of an OFDM symbol. Accordingly, the single-frequency network is utilized in digital video broadcasting (DVB) systems.